Intermittent PHP Abstract Class Error

Question

I've been fighting this for a bit, and can't figure it out, maybe someone else has or maybe there's a deeper issue here with Slim, PHP, Apache etc. After working just fine for hours, my Slim install will start giving this on all routes:

Fatal error: Class Slim\Collection contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (IteratorAggregate::getIterator) in F:\Projects\example\server\vendor\slim\slim\Slim\Collection.php on line 21

Maddeningly this issue goes away if I restart Apache. (For a few hours anyway.)

I found this where someone had a similar problem two years ago, and the person helping badgered them without actually assisting at all: https://community.apachefriends.org/viewtopic.php?p=250966&sid=96ef58aaeb7fe142a7dcdfd506a8683f

I've tried doing a clean wipe and install of my composer vendor directory. This doesn't fix it. I can clearly see that getIterator is implemented as expected in the file in the error message.

PHP Version 7.0.12, Windows 7, x86 PHP Build

It happened again after a few hours, with a different but similar error message:

Fatal error: Class Pimple\Container contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (ArrayAccess::sqlserver) in F:\Projects\example\server\vendor\pimple\pimple\src\Pimple\Container.php on line 34

This question has a similar problem and "solves" it by restarting PHP, but that clearly isn't an actual solution, and I don't have opcache enabled: PHP 7, Symfony 3: Fatal error 1 abstract method and must therefore be declared abstract or implement the remaining methods

Any guesses? Remember: This message is in files I didn't write, and goes away on Apache restart. Is there some caching with PHP 7 that would cause this?

Edit 3/10/17:

Yes, I've opened a ticket with Slim. I also saw it in a non-slim file (Pimple) so I don't think it is a Slim issue. https://github.com/slimphp/Slim/issues/2160

As I said, my opcache is off. I've confirmed this is true both in the php.ini file and looking at phpinfo().

Answer 1

I think you've run into this opcache bug. This isn't exactly the same situation but probably related.

After calling opcache_reset() function we encounter some weird errors. It happens randomly on servers (10 of 400 servers production)

Some letter a replaced by others, Class seems to be already declared.. etc

Example of errors triggered after opcache_reset():

• PHP Fatal error: Class XXX contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (YYY::funczzz) in /dir/dir/x.php on line 20

The ticket is closed because the developers don't have enough information to reproduce it. If you could come up with the smallest reproducible case I recommend reporting it. Create a very small Slim app and then use JMeter or another tool to make many requests. Post your findings.

Meanwhile the only workaround might be to turn off opcache in php.ini:

opcache.enable=0

Of course this will drastically hurt performance. Until it's fixed you'll have to choose between performance or periodically restarting Apache.

If turning the cache off doesn't work then the only cause I could think of is an intermittent problem with the opcode compiler. Cached or not the compiled version must have an error in it. Opening a reproducible ticket with the PHP devs or debugging the PHP source yourself would be the only way forward if this is the cause.

Answer 2

I had the same problem using CodeIgniter and PHP 7.1.x.

I upgraded to PHP 7.2 and the problem no longer occurred.